Solubility of Silicon Nitride into RE (RE=Y, Gd, Nd and La)-Mg-Si-O-N Melts and Hardness of Glasses

Abstract

The solubility of α-silicon nitride into RE₂O₃ (RE=Y, Gd, Nd and La)-MgO-SiO₂ melts have been examined systematically. The effect of nitrogen content on the Vickers hardness of RE-Mg-Si-O-N oxynitride glasses have been examined.
The dissolution reaction of α-silicon nitride into melts have achieved equilibrium about 6 h holding at 1773 K. The content of saturated nitrogen was 4.8∼5.8 at%, depending on the ionic radius of adding rare-earth elements. A marked change was observed in the order of ionic radius from La to Y.
The Vickers hardness of RE-Mg-Si-O-N oxynitride glasses increased with increasing the content of nitrogen. The results from X-ray photo-electron spectroscopy of oxynitride glasses revealed the existence of Si≡N bonds. These results suggest that the substitution of nitrogen for oxygen may lead to the increase of cross-linking produces a more rigid glass network.